The overrunning clutch to which the present invention is directed, is of the type set forth in my U.S. Pat. No. 4,869,357 issued Sept. 26, 1989 and entitled Overrunning Clutch with Grooved Bushing for Reception of Spring Coil. In the overrunning clutch of my prior patent, preferably the cylindrical bushing member included at least one groove of a depth and width to fully accommodate a coil spring within the inner periphery of the bushing with the spring, when relaxed, having an inner diameter slightly larger than the diameter of the shaft member projecting axially through the bushing member. With the coil spring fixed relative to the bushing so as to be nonrotative, the coil spring has at least one free end in frictional engagement with the periphery of the shaft. Relative rotation of the bushing and the shaft in one direction causes multiple turns of the coil spring to engage the periphery of the shaft and to snub the spring, and to thereby cause a driving member to rotate a driven member as fast as that of the driving member. Additionally, the driven member is permitted to rotate faster and free-wheel to overrun the driving member.
While such overrunning clutches as exemplified by my prior U.S. Pat. No. 4,869,357 have operated satisfactorily, I have determined that the torque transmitting capacity of the coil spring overrunning clutch may be greatly increased by using a larger diameter spring wire. However, there is required a significantly increased radial force on the shaft by the free end of the spring to initiate the snubbing action due to the increased stiffness in the spring wire as a result of the increase in diameter of the same. When such radial force becomes too large, it can cause the spring wire to score or abrade the shaft.
In U.S. Pat. No. 4,313,530 issued Feb. 2, 1982 to Boyd and entitled Brake Actuator for Bicycles and the Like, a solution to the problem of scoring or abrading the shaft involves the welding of leader springs of wires having a relatively small diameter to the axially inboard ends of a number of turns of wire of larger diameter, acting as the load carrying wire of the clutch. However, the connection between such two high carbon steel wires is bulky, cumbersome, and results in less than a 100% strength of connection. Such overrunning clutch structures are subject to failure, particularly since the heat of welding draws the temper of the wires.
It is therefore a primary object of this invention to provide a single, unitary coil spring for overrunning clutches including a relatively large diameter load carrying coil terminating in turns proximate to the free end of the coil spring whose radially outer or radially inner peripheries are ground down to render these turns less rigid and to facilitate the initiation of the snubbing action for the clutch.
It is a further object of the invention to provide a simplified mounting of a double spring coil having dual free ends, received within respective adjacent, parallel helical grooves, within the inner periphery of the bushing or the outer periphery of the shaft, irrespective of whether the spring coil terminates in turns proximate to the free end whose outer or inner peripheries are ground down to facilitate free end functional engagement with the periphery of the shaft or bushing.